It is known to employ passive water stop devices in the joints or gap openings arising between concrete building structure members, such as floor slabs and wall-floor segments which are sequentially formed. For example, a concrete floor slab is cast; then an adjacent floor slab or wall segment is subsequently cast against it. As concrete shrinks during curing, a gap opening can arise in the construction joint between these separately formed concrete members. There is an opportunity for water to pass through the joint, especially in sub-grade installations. A plastic sheet or steel member can be located within this “cold joint” or gap opening, so as to create a tortuous path for impeding the travel of water into or out of the structure.
It is also known to employ active water stops that swell upon contact with water from the inside or outside of the concrete structure, such that the water stop expands to fill up the joint or gap opening and thereby prevents water from entering or exiting the concrete structure. Aqueously-swelling water stop designs are disclosed in European Application Publications No. 0 050 906 A1 of Ishido et al. (Application No. 813000341.5); No. 0 037 717 A1 of Yamaji et al. (Application No. 81301443.8); and No. 0 160 448 A2 of Harriett (Application No. 85302656.5).
In the aforementioned EP No. 0 050 906 A1 (owned by Hayakawa Rubber Company), Ishido et al. disclosed a sealing process using an aqueously-swelling sealant composition comprising 10 to 40 weight percent of rubber whose main ingredient is “reclaimed” rubber, 10 to 20 weight percent of silicic compound, 10 to 60 weight percent of bentonite, and 10 to 40 weight percent of plasticizer. It was taught that this composition could be extruded with or without a core therein, and could be inserted into a joint gap or other gap of structure members to stop water at the gap. (See also U.S. Pat. No. 4,366,284 of Ishido et al.).
In EP No. 0 037 717 A1 (also owned by Hayakawa), Yamaji '717 A1 et al. disclosed a water stopper having an aqueously-swelling water-stopping composition consisting of 10 to 40 weight percent of rubber whose main ingredient is polyisobutylene, 10 to 20 weight percent of silicate, 10 to 60 weight percent of bentonite, the silicate and bentonite acting as “fillers,” and 10 to 40 weight percent of plasticizer. This is extruded into an elongate water stopper, with or without a core therein, for use in a joint gap.
In EP No. 0 160 448 A2, Harriett disclosed a composition comprising bentonite intimately contacted with polypropylene, polybutylene, or mixtures thereof, which could be extruded into a rope, rod, or other shape for preventing water seepage in a gap.
In US Patent 2011/0042613, Loehner et al. disclosed a water-swellable composition containing hydrophilic cross-linked polymer particles.
In EP No. 0 900 834, Tagoshi et al. taught a water-swellable elastomer composition containing N-vinylcarboxylic acid amide-based cross-linked resin and a water-swellable polyurethane.
To ensure good water sealing performance, however, it is imperative that the aqueously-swellable water stop maintain continuous contact over its entire length with the concrete surrounding the construction joint. As the density of concrete is higher than the density of these prior art water stops, the water stop will tend to float in the wet concrete that is poured against previously installed concrete; and this sometimes results in the rubber water stop being dislodged so that it “snakes” (or curls). This snaking or curling is amplified by the tendency of the water stop to expand in contact with the water of the wet concrete, immediately after casting of the concrete. The expansion of these prior art water stops is a tri-dimensional process; or, in other words, the water stop will not only swell in height and width but it will also tend to increase in length.
Snaking can result in concrete flowing between the water stop and the first poured concrete, giving rise to a separate construction joint (or gap opening) which cannot be plugged by the water-stop device. Risks of water seepage thus increase.
A contact adhesive can be used to keep the water stop in place while the subsequent concrete structure is cast against it and allowed to cure in place. However, as the grip of the adhesive builds slowly in most situations, the practice hitherto for ensuring that the water stop stays in place during the pouring and curing of the concrete (especially in vertical and hanging applications) is to drive a nail through the water stop every 20-30 centimeters. However, it is time consuming to ensure such contact adhesive is applied correctly along the full length of the waterstop, to allow for curing and to drive nails through the water stops. Also, such contact adhesives do not work well if the concrete surface becomes wet due to rain during curing.
Another solution is to install a metal mesh or cage over the water stop and fasten it against the concrete at 20-30 cm intervals. This kind of installation is unsatisfactory where steel rebar intrudes into installation space or other irregularities exist.
Overall, the need to use contact adhesive, cages, nails, and other fasteners means time-consuming, highly labor-intensive work such that the quality of the job will depend upon diligence and skill of the applicator. Nails and cages cannot be used in installations that require sealing around pipes, moreover. The water stop must be kept in place by means of metal wires. Again, this increases the labor required for installation as well as the dependence upon the diligence and skill of the applicator for success of the job.
In view of the foregoing disadvantages of the prior art, the present inventors believe that a novel and inventive water stop design and method for concrete construction joint water stopping are sorely needed. Such an improved water stop needs to resist the deformation of the water stop body which tends to destroy or to disrupt continuous contact between the water stop and surrounding concrete within the construction joint or gap opening.